I agree with the drive definitions. The thing is, no matter what kind of drive the dog is in, the other drives exist within the same dog. The amount and influence they have on the pronounced drive varies from dog to dog. The other drives do have an influence and it is an observable influence.
The nice thing about prey and defense drive is both can be built. Like someone mentioned in other postings it is the situation that brings the dogs drive into play. You have got to have one component to have the other.
You will have no argument from me that some dogs are more inclined to work in defense drive over prey drive because i know it is true.
Still it is not black and white as to why. I try to think of it like this:
I take into account all the drives in a dog and think of a sliding color scale for each one. 1 being weaker influence and 100 being the highest influence.
(I am working on a color program that represents such an effect. It is like the Red Blue and Green color bars that give color a # value. This maybe to complicated to write about without being able to demonstrate it.)
I just know prey drive and defense drive can be built though conditioning. I also know they influence each other even if the dog seems to have no chase behavior in him, he does. It is just that drive is suppressed or has a very small value so its influence is less distinguishable.
I know each dog by their temperament will have both prey and defense drives and a sort of base level for each that is biological.
Prey and defense can be build up or torn down through conditioning with each dog having its limit (threshold) to how much it can be influenced or before the drive changes. I call this quality: Drive Resiliency.
Fight drive is all about confidence and the dogs ability and willingness to win. He needs to have a minimum and relatively high level of both prey and defensive drives combined with experience before you will see true fight drive in action.
Getting back to the original question I had... The dog must one close his mouth before the catch and 2 the dog will demonstrate a quite focus just before the grab.
Some dogs are vocal right up to the bite and as most people on this forum know we can and do train them to be vocal right up to the bite like in the Hold & Bark.
Yet even in the H & B, we can observe in a split second interval between the dog's last bark and the actual bite. In this time frame his mouth will close and he focuses all concentration just before the strike. All dogs have different drive strengths influencing them. Because some of that strength is genetic we can observe breed traits. Perhaps it also explains why so there is a latency issue that varies in this species specific behavior. (closes its mouth and focuses before biting)
At least that is the thread of my thinking.
This topic has been more for the behaviorist out there and like others have mentions one doesn't need to know all the terms and nuances to be a good and effective trainer. To me the nuances are interesting because I think their study can at times reveal new or better understandings about the dog that can in turn improve your training even if it doesn't apply to your current training goals.
A dog teaches a boy fidelity, perseverance, and to turn around three times before lying down. - Robert Benchley
In order to really enjoy a dog, one doesn't merely try to train him to be semi-human. The point of it is to open oneself to the possibility of becoming partly a dog. - Edward Hoagland